1. Field of the Invention
The present invention relates to an image pickup module that includes a lens element having a flange part that is integral with the lens element and, in particular, relates to a small and thin image pickup module that is suitable for use in an endoscope. Also, the present invention relates to an image forming lens that includes a lens element having a flange part that is integral with the lens element, for use with an image pickup module.
2. Description of the Related Art
In conventional image pickup modules it has been proposed that, in order to reduce costs and manufacturing errors, some lens elements of the image pickup module be formed integrally with a flange part so that the number of components may be reduced, thereby improving the ease of assembly of the image pickup module. One such image pickup module, for example, is disclosed in Japanese Laid-open Patent Application No. 2003-46825. On the other hand, in an image pickup module suitable for use in an endoscope, etc., it has been required that the diameter of the image pickup module be as small as possible in order to minimize the burden to a patient and to improve an operator's performance. Therefore, in an image pickup module that includes a lens element having a flange part that is integral with the lens element, it is particularly important to miniaturize the outer diameter of the image pickup module as much as possible. However, with respect to the conventional image pickup module equipped with a lens element integrally formed with a flange part as disclosed in Japanese Laid-open Patent Application No. 2003-46825, nothing has been proposed for miniaturizing the outer diameter of that lens element.
In general, in an image pickup module that includes a lens element having a flange part that is integral with the lens element, at the time of assembly of the image pickup module, positional adjustment of the lens element in the axial direction is usually achieved by abutting one end of the lens element that is formed integrally with a flange part to the image pickup surface of the image pickup element. Accordingly, in order to obtain a high accuracy in positioning the lens element in the axial direction, a high accuracy in manufacturing the lens element that is formed integrally with the flange part is required.